There is known a hybrid construction machine such as a power shovel with an engine and a motor generator. The hybrid construction machine generates electric power by rotating a generator by means of an excess output of the engine, and/or generates power by rotating the motor generator by means of energy discharged from an actuator. The power generated in this way is used to rotate the motor generator, and a hydraulic motor and the like are driven by means of the rotation of the motor generator.
JP2009-235717A discloses a control device for a hybrid construction machine that utilizes a turning pressure of a turning motor as regenerative energy. This control device causes a fluid pressure motor to rotate by utilizing the turning pressure of the turning motor, thereby rotating a motor generator to generate electric power or actuating an assist pump coupled to the fluid pressure motor.